Adaptive clutter suppression based on iterative adaptive approach for airborne radar

To improve the performance of the recently developed weighted least-squares-based iterative adaptive approach (IAA) in space–time adaptive processing (STAP) for weak or slow targets detection, we propose a novel IAA scheme to adaptively suppress the ground clutter by using the secondary training data (STD). Especially, we use the IAA to estimate the clutter plus noise covariance matrix from a very small number of STD. The resulting clutter plus noise covariance matrix can be utilized to form the STAP filter and then suppress the clutter. To reduce the computational complexity of the IAA, we exploit the sparsity of large clutter components in the angle-Doppler image and develop a modified IAA algorithm employing a soft-thresholding to adaptively determine the entries of each iteration that should be updated. Simulation results show that our proposed scheme outperforms the conventional IAA scheme over weak or slow targets detection and the modified IAA algorithm exhibits a comparable or even a better performance than the IAA algorithm but a lower computational complexity.     

悬浮粒子浓度测定的实验室间比对试验分析

通过对检测实验室间悬浮粒子浓度的比对试验进行分析,以准确了解参加比对的人员和仪器的工作状况,验证相关实验室悬浮粒子浓度的检测能力,确保空气洁净度检测结果的质量.     

机载海洋激光雷达系统的有效衰减系数

本文利用蒙特卡罗模拟技术，研究了有衰减系数Г与飞机高度Ｈ和视场角ＦＯＶ等系统参数以及体积衰减系数ｃ和单次散射率ω０等水质参数的关系，首次得到了系统最小有效衰减系数的近似计算公式，该公式给出了系统参数乘积足够大时Г与水质参数ｃ，ω０之间的定量关系，为海洋激光雷达系统的设计提供了有力的依据。     

Airborne Wide Band Coherent Radar for Ice Thickness Measurement

A prototype of an airborne wide band coherent radar has been accomplished which can be used for polar ice thickness measurement. The system uses pulse compression and coherent integration techniques and works at the VHF band. Using different transmit power, the radar can operate in both surface-based and airborne applications. The chirp waveform generator was designed by using a Direct digital synthesizer （DDS）. A dual-channel receiver was introduced for better performance on the return signals of different layers. Surface-based experiments were done to test the system performace.     

技术标准的前瞻性与实践的互动性讨论

从我国技术标准国际化、产业调整升级和创新发展的推手角度,浅谈技术标准的前瞻性以及实践过程中的互动性,同时说明建立我国洁净室及相关受控环境标准体系的紧迫性。     

洁净室气态分子污染物的监测技术

随着微电子工业工序复杂性的增加和产品尺寸的不断缩小,气态分子污染物(AMC)对产品的影响成为洁净室环境控制中重点关注的问题。文章介绍了洁净室中AMC的定义,重点阐述了AMC的监测技术。     

Evaluation of reactive oxygen species generating AirOcare system for reducing airborne microbial populations in a meat processing plant

The microbial contamination of meat and meat products is of continuing concern to the meat industry and regulatory agencies. Air has been established as a source of microbial contamination in slaughter and processing facilities. The objective of this research was to determine the efficacy of reactive oxygen species (ROS) generating AirOcare equipment in reducing airborne bacteria in a meat processing environment. Bacterial strains found in ground beef were used to artificially contaminate the air using a 6-jet Collison nebulizer. Airborne bacterial populations in the meat processing room were monitored every 24 h at multiple locations using a Staplex 6 stage air sampler. Total aerobic, Gram-negative, and lactic acid bacterial populations were determined by sampling on R₂A agar, MacConkey agar and Lactobacilli MRS agar, respectively. Approximately 3 log reductions of lactic acid bacteria and Gram-negative bacteria were observed after 24 h of treatment (p < 0.05) compared to ~1.5 log reduction in the control treatment. Further exposure with ROS significantly reduced lactic acid bacteria and Gram-negative bacteria in the air at 48 and 96 h sampling intervals. These findings reveal that reactive oxygen species treatment using AirOcare unit significantly reduces airborne contamination in a meat processing environment. Mention of trade names or commercial products does not imply recommendation or endorsement to the exclusion of other products by the U.S. Department of Agriculture.     

一种快速的全波形高光谱激光雷达的反射率光谱曲线重建方法

全波形高光谱激光雷达(HSL)在获得高精度、高分辨率的空间数据的同时,还能获得目标的光谱信息,可为不同研究和应用领域提供有效和多维的数据。然而,HSL不同波段发射信号强度存在差异,会导致相应回波信号的差异,难以直接利用回波信号来重建目标在不同波段下准确的光学特性(目标的反射率光谱分布曲线)。以往研究通常利用标准漫反射白板法来获取目标的反射率光谱曲线(标准参照板法)。但在某些复杂的检测环境中白板易受污染,且激光器的发射能量会因环境和设备状态的变化出现波动,进而影响计算精度。因此,从全波形信号本身直接提取信息用于反射率光谱曲线重建是一种快捷的途径。基于此,该文提出一种基于HSL全波形数据的回波强度校正方法,用于快速生成目标的反射率光谱曲线。首先,通过理论分析,证明回波与发射波在形状上的相似性。然后,对HSL全波形的发射信号和回波信号进行偏正态高斯函数拟合,计算各波段在理想情况下标准漫反射白板的发射信号与回波信号峰值比值(归一化因子)。最后,通过结合标准漫反射白板的归一化因子与目标的归一化因子来构建目标的反射率光谱分布曲线。为验证方法的有效性,该文将其与基于标准漫反射板计算的反射率光谱曲线进行了对比实验,并进行木叶分离和目标分类实验以评估其适用性。实验结果表明：(1)利用发射信号校正回波强度,可以获得与标准参照板法相似的反射率光谱曲线。并且在不同温度及光照条件下均表现出良好的稳定性;与标准漫反射白板法相比,该方法有效克服了激光器发射能量波动的影响,尤其在HSL长时间工作条件下,显著提升了反射率光谱曲线的测量精度和一致性。(2)在实际应用中,基于该文方法获得的目标反射率光谱曲线能够快速实现木叶分离,且对果树目标分类准确率超过90%。该文方法简化了全波形高光谱激光雷达的回波强度校正流程,可在数据采集过程中实时快速重建目标高光谱信息。     

复杂天气下车载激光点云目标检测方法综述

随着传感器、数据处理、视觉感知、控制决策、人工智能等自动驾驶相关技术的不断发展,自动驾驶成为汽车行业未来发展的重要方向之一.但是,以雨、雾、雪等复杂天气为典型代表的极端驾驶环境,对自动驾驶环境感知提出了严峻挑战.随着激光雷达（Light detection and ranging,LiDAR）在汽车上得到广泛运用,基于车载激光点云的目标检测已成为自动驾驶环境感知的重要研究方向之一,但在复杂天气条件下,LiDAR探测生成的点云存在大量噪点,对目标检测的性能产生严重负面影响.对此,本文首先归纳了点云目标检测的基本定义、任务方法和评测指标,然后分析了复杂天气对点云目标检测的影响,并从数据增强、点云去噪、域自适应以及传感器融合等四个方面,系统分析了复杂天气下基于车载激光点云的目标检测方法及其优缺点,最后探讨了当前存在的数据规模与真实性不足、模型结构复杂、数据分布不均匀、实际部署瓶颈等问题以及未来研究方向.